While a hydrocarbon well is often no more than a foot in diameter, overall operations at an oilfield may be quite massive. For example, even in the case of offshore operations, with footspace limited to a discernable platform, the amount of manpower, expense, and equipment involved may be daunting. This is particularly true when considering everything involved in drilling, completing and managing a productive well. Indeed, as described below, the amount of noise alone from such operations may present considerable challenges.
Noise generated by the surface equipment involved in oilfield operations is often quite significant. For example, well management and interventional equipment such as coiled tubing is often directed through use of high pressure pumps which are in turn driven by large engines. These engines may be large scale diesel engines which, under normal operating conditions, exceed about 115 dB in noise output. Unfortunately, in many jurisdictions, this level of noise exceeds acceptable statutory thresholds, generally set at about 90 dB. For example, populated areas near the North Sea, may prohibit near offshore employment of equipment exceeding such noise output. Furthermore, even in absence of nearby population centers or statutory regulation, such noise output may pose a health hazard to operators at the well site. This is particularly true in the case of ongoing operations where such equipment is likely to be run on a near-continuous basis for days on end. For example, this may be a likely scenario for coiled tubing interventions directed at a well location several thousand feet into the well.
In order to reduce health hazards to operators and keep noise level at acceptable statutory levels, efforts have been made to dampen or reduce the decibel level emanating from such equipment. Generally such damping involves positioning of the equipment within a thick walled housing. As such, layers of walls may serve to reduce the amount of sound or noise which travels beyond the housing. For example, in most cases, layers of stainless steel or other suitable material walls may be used for a housing that effectively dampens an engine noise output of about 115 dB to less than 100 dB as perceived from outside of the housing.
Unfortunately, damping through use of a flat walled housing has its practical limits. That is, the amount of damping achieved through such means is inversely exponential to the thickness of the walls. So, for example, depending on the materials used, each decibel reduction attained may be accompanied by a doubling in wall thickness of the housing. Thus, ultimately, in order to reduce a 115 dB output to less than about 90 dB as described above, an immense, expensive and completely impractical housing would need to be constructed. Even mobilizing such a housing and engine at the well site would not be practical, particularly in the case of offshore operations.
As an alternative to damping through use of flat walled housings, sound proofing may be attempted through use of more sophisticated wall architecture. For example, spherical attenuator designs, often referred to as Helmholtz designs, may be employed where spherical bodies are effectively imbedded throughout the housing walls. This may be achieved by providing an array of semi-spherical scoops or indentations into each wall layer. Subsequently, the walled layers may be precisely aligned relative to one another such that an array of spheres is effectively disposed between the adjacent layers.
Furthermore, an added level of complexity may be provided with each and every sphere being provided with its own inlet channel. Such channels may be provided in conjunction with the forming of the semi-spherical indentations. Of course, in order to provide only a single inlet channel per sphere, only half of the indentations, perhaps those of just one of the layers, would be provided with the channel. That said, more complicated inlet channel formation may certainly be employed, such as where channels are provided at alternatingly opposite sides of the spheres. Regardless of the particular design and complexity, such spherical resonators are vastly more effective as compared to flat walled attenuation described above.
Unfortunately, while very effective at damping noise, for example from 115 dB to well below 90 dB, the expense of constructing a spherical resonator large enough to serve as a housing for oilfield equipment remains impractical. That is, while practical in terms of wall thickness, a spherical resonator large enough to house a coiled tubing engine, for example, may run several hundred thousand dollars or more due to the level of sophistication required in construction. As a result of such impractically large and/or expensive alternatives, operators of such high noise equipment are primarily left with the option of operating below capacity to keep noise levels within safe and statutory limits.